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SS2 Chapter 1.pptx
- 2. Insolation Solar energy reaches earthin the form of Short waves. This is called as insolation.
- 3. Processes of heattransfer in the atmosphere
- 4. Terrestrial radiation. The re-radiationof energy from the surface of the earth back to the outer space in the form of long waves is called terrestrial radiation.
- 5. Heat budget Thebalance between insolation and terrestrial radiation is called heat budget. Entire energy reaching the earth's surface is returned to the outer space through various means. Through this heat balancing process termed as heat budget, the surface temperature of the earth is kept balanced.
- 6. Temperature Temperature is thedegree of hotness of the atmosphere. It is from the weather condition at 2pm that the meteorologists measure the maximum temperature of a day. The minimum temperature is taken just before the sunrise.
- 7. Diurnal range oftemperature. The difference between the maximum and the minimum temperatures of a day is called diurnal range of temperature. Diurnal range of temperature = maximum temperature of the day – minimum temperature of the day
- 8. Daily mean temperature. The average temperature of a day is termed Daily mean temperature. Daily mean temperature = Maximum temperature + Minimum temperature 2
- 9. Isotherms The imaginary linesconnecting places having equal atmospheric temperature are called isotherms. Temperature varies from place to place on the earth's surface.
- 10. Factors influencing thedistribution of temperature:- Latitude. Altitude. Nearness of ocean. Winds.
- 11. Latitude The regionreceives more energy as the sun's rays are almost vertical. The sun's rays becomes more inclined on approaching the poles. There occurs more energy loss as the sun's rays have to travel more through the atmosphere owing to the inclination.
- 12. Altitude • Temperature inthe troposphere decreases at the rate of 1° C per 165 m of altitude. • The temperature is comparatively low at places situated much above the sea level.
- 13. Nearness of Ocean The range of temperature will be high at places away from the sea and vice versa. Temperature remains moderate at places close to the sea. This is because the heating of land causes wind to blow from sea to land and cooling of land causes wind to blow from land to sea.
- 14. Winds The warmand the cold winds can respectively raise or lower the temperature of the places through which they pass.
- 15. Water in theatmosphere Humidity :- Water content in the atmosphere is called humidity. Factors influencing the amount of moisture in the atmosphere :- Temperature. Nearness to sea. Presence of water bodies.
- 16. Absolute Humidity. Theactual amount of water present in the atmosphere is called absolute humidity. It is measured as the amount of water vapour present per cubic metre volume of air (g/m3).
- 17. Saturation level. Thereis a limit to the amount of water vapour the atmosphere can hold at a certain temperature. The stage at which the atmosphere is fully saturated with water is termed as saturation level. When the atmosphere becomes saturated , condensation begins.
- 18. Dew Point The criticaltemperature at which condensation begins is called dew point.
- 19. Relative Humidity Theratio between the amount of water vapour present in the atmosphere and the total water holding capacity of the at mosphere at a given termperature is called relative humidity. If the absolute humidity is half of the total water holding capacity at a particular temperature, then the relative humidity will be 50%. Relative Humidity = Absolute humidity * 100 Total water holding capacity of th atmosphere at that particular temperature.
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- 21. Dew The surface ofthe earth gets cooled during the night and it cools the near atmosphere. This causes the water vapour to condense and the condensed droplets cling on to the cold surfaces on earth.
- 22. Frost There are placeson the earth were the night temperature falls below 0° Celsius. Tiny ice crystals are formed in such places. This form of condensation is called frost.
- 23. Fog or Mist Fog or mist is the result of condensation around the minute dust particles in the lower atmosphere. If the range of visibility is less than one kilometre, it is termed fog. If the range of visibility is more than one kilometre, it is called mist. Fog Mist
- 24. Clouds Clouds are formedby the condensation of water vapour around the fine dust particles in the atmosphere.
- 25. Different types ofclouds :- Cirrus Clouds. Stratus Clouds. Cumulus Clouds. Nimbus Clouds.
- 26. Cirrus Clouds These arefeather-like clouds in the upper atmosphere in clear weather conditions.
- 27. Stratus Clouds These appearin thick layers in the lower part of the sky.
- 28. Cumulus clouds :- Theseclouds resemble huge cotton bundles and are formed due to strong convection currents. They have large vertical extent.
- 29. Nimbus clouds :- Theseare dark rain clouds in the lower atmosphere. These clouds appear dark as it does not allow sunlight to pass through due to thick concentration of water droplets.
- 30. Different types ofclouds based on altitude. High clouds (20000 to 40000 ft) Medium clouds (7000 to 20000 ft) Low clouds (< 7000 ft) Clouds with great vertical extent (2000 to 30000 ft)
- 31. Precipitation Continuous condensationcauses the droplets in the clouds to grow in size. Being unable to resist the gravitational force of the earth, the water droplets get released from the clouds and fall on the earth in different forms. This process is called precipitation. Different forms of precipitation :- . Rainfall . Snowfall . Hailstone
- 32. Rainfall The common manifestation of precipitationis in the form of water drops. This is the rainfall.
- 33. Snowfall When the temperature fallsbelow 0° Celsius, precipitation reaches the earth in the form of tiny crystals of ice. This is snowfall.
- 34. Hailstone If the waterdroplets released from the clouds happen to pass through colder layers of the atmosphere, they may reach the earth in the form of ice pellets. This form of precipitation is called hailstones.
- 35. Different types ofrainfall. Orographic rainfall The moisture-laden wind from the sea enters the land and moves upwards along the mountain slopes where it gets cooled and condensed to form clouds. When the windward sides of the mountain receive heavy rainfall, the leeward sides do not receive rainfall due to the descending dry air. This type of rainfall is known as orographic rainfall or relief rainfall. Convectional rainfall Cumulus clouds are formed by the cooling and condensation of rising warm air. Rainfall occurs with thunder and lightning. This rain, mostly occurring in the afternoon , does not last long. This type of rainfall is called convectional rainfall. . Border Rainfall There is always a difference in the atmospheric temperature over land and sea. If the air over the sea comes in contact with the air over the land in the coastal regions, the warm air will be pushed upwards causing cloud formation and rainfall. This type of rainfall is called border rain.
- 36. Different types ofrainfall Orographic Rainfall Convectional Rainfall